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Old 01-06-2010, 08:32 PM   #21
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What I do is seal the keg while empty hit it with a blast of Co2 then purge, repeat 3 times.
Fill the keg from the Out post - purge one or two more times and I am done.

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Old 01-06-2010, 08:50 PM   #22
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Originally Posted by Bobby_M View Post
I flood the keg with CO2 for one minute with the lid off, rack the beer in to the bottom gently, seal it, flood it, vent it. If there's still O2 in there after that, F it.
For real, I have used this and kept beers on tap for months with no ill effects.

I have even transferred commercial keg beer into cornies using the same method and it has kept for quite awhile at least until it was consumed.
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Old 01-06-2010, 08:58 PM   #23
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Quote:
Originally Posted by Dr Malt View Post
Remilard:

In a bottle, air can diffuse under the cap resulting in O2 in the head space. The major brewers use oxygen scavenging caps to absorb this oxygen to extend shelf life. So whether the yeast are consuming all the O2 or it is equalibrium with diffusion is a question. I know that active brewers yeast in a closed container removes O2 to less than 1 ppb.

Dr Malt
Well obviously there is a limit to how much oxygen yeast can scavenge. A fermenting carboy in a closed room will not remove the oxygen in the room.

Various sources, George Fix come to mind, have reported that the yeast in bottle conditioned beers scavenges less than half of the oxygen present in the headspace. I would certainly entertain information to the contrary.
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Old 01-07-2010, 09:14 PM   #24
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I thought we were discussing how to remove O2 from a closed corny keg. Where did removing O2 form an entire room come from??

Yesat in an enclosed container like a corny keg or sealed conical fermenter will lower the O2 in the liquid to less than 1 ppb. I know this as we measure the O2 on 8000 gallon fermenters every day.

Dr Malt

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Old 01-07-2010, 09:40 PM   #25
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Originally Posted by Dr Malt View Post
Yesat in an enclosed container like a corny keg or sealed conical fermenter will lower the O2 in the liquid to less than 1 ppb.
I'm just beginning to understand this subject, but noticed the highlighted words. This is true, I don't think anyone's arguing it. The yeast will take up oxygen in the beer while they're active, but what about the oxygen absorbed from the headspace after they run out of sugar? They won't actively pull oxygen from the headspace, so it's going to diffuse at a normal rate, which will keep happening long after the yeast go dormant.
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Old 01-07-2010, 09:54 PM   #26
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Quote:
Originally Posted by Dr Malt View Post
I thought we were discussing how to remove O2 from a closed corny keg. Where did removing O2 form an entire room come from??

Yesat in an enclosed container like a corny keg or sealed conical fermenter will lower the O2 in the liquid to less than 1 ppb. I know this as we measure the O2 on 8000 gallon fermenters every day.

Dr Malt
Quote:
Originally Posted by Scimmia View Post
I'm just beginning to understand this subject, but noticed the highlighted words. This is true, I don't think anyone's arguing it. The yeast will take up oxygen in the beer while they're active, but what about the oxygen absorbed from the headspace after they run out of sugar? They won't actively pull oxygen from the headspace, so it's going to diffuse at a normal rate, which will keep happening long after the yeast go dormant.

I am interested in the answer to this question. Does priming with sugar help reduce oxygenation vs. force carbing?
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Old 01-12-2010, 01:09 AM   #27
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Thanks for all your answers to this question. Happily, for me at least, I have found the answer about how fast O2 diffuses through CO2. I had a conversation with a colleague of mine who is a PhD material scientist, and she handed me a book written by one of her professors at the University of Minnesota. The book is called “Diffusion, Mass transfer in fluid systems”. Lest you doubt me, the author is E. L.Cussler, and it’s published by Cambridge Press.

Working through the chapters on gas-gas diffusion, not only did I realize why I am not an engineer, but I came across a table of diffusion constants for gas pairs, and more important, an equation to calculate penetration distance of the diffusing gas as a function of time, as room temperature and one atmosphere pressure. So, armed with my calculator, and the table I calculated the distance O2 diffuses into CO2 in one second, one minute and one hour. The answers surprised me.

The equation is quite simple, and the assumptions are too, RT, one atmosphere pressure, no convectional mixing. Distance (Z) is in centimeters, time (t) in seconds, diffusion constant is D. The equation is –

Z = the square root of (D x t)

D for O2 into CO2 is 0.16 cm squared/second

So, in the first second Z is 0.4 cm
First minute Z is 3.0 cm
First 5 minutes Z is 7.0 cm
First hour Z is 24 cm

I was surprised that the diffusion is as slow as it is. Even in an hour, O2 won’t penetrate to the bottom of a corny keg if it’s in the air being pushed out of the keg by a CO2 purge.

Subsequently I looked at gas diffusion into liquids, and it is generally about 10,000 times slower. For example O2 in water, the diffusion constant is 2.1 x 10 to the -5 power. So in one minute O2 diffuses only 0.0126 mm or 0.5 thousandths of an inch. Assuming no mixing…

So, as I thought about this, I realized that the any method we have been using to purge air from corny kegs will be fine, as long as air or O2 don't get much time to diffuse into the beer.

Now, I realize this argument is based on ideal conditions, and the real world is less than ideal with different temperatures of gases and liquids, mixing of gases regardless of how careful we are, and so forth, but this does help me get a grip on this issue. I also realize that in the real world, careful homebrewers rarely experience oxidation related problems in their beer. And this makes sense to me, because the common thead to most of the method folks described don’t give the beer time to pick up appreciable amounts of O2 by purging before or immediately after racking.

This also explains the reason we shake our kegs to carbonate quickly: to expose fresh liquid to the CO2 because leaving it on it own to diffuse through 18 or so inches of beer in a corny with no mixing is dead slow.

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Old 01-12-2010, 02:23 AM   #28
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Originally Posted by AiredAle View Post
At this point, I think I will switch from purging air filled cornies to sanitizer filled cornies. No math needed, just displace the maximum amount of air with water and then displace the water with CO2.

So, thanks to all for the ideas.
But when you blow the water out, won't there be little drops
still clinging to the side, and those drops will have 02 dissolved
in them, unless you boil it first and then cool it under an
inert atmosphere? Or maybe you could buy a shed, airtight
it, then put some giant CO2 cylinders outside and purge
the entire building, and do your brewing in a spacesuit?
Jim
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Old 01-12-2010, 02:29 AM   #29
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Originally Posted by remilard View Post
Various sources, George Fix come to mind, have reported that the yeast in bottle conditioned beers scavenges less than half of the oxygen present in the headspace. I would certainly entertain information to the contrary.

The oxygen in the headspace isn't doing anything. Nothing happens
until it dissolves in the liquid and a reaction can take place. So you really
need to know how much of the O2 in solution gets taken up. I would guess
all of it until the yeast dies or becomes dormant.
Jim
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Old 01-12-2010, 02:47 AM   #30
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Quote:
Originally Posted by AiredAle View Post
The equation is quite simple, and the assumptions are too, RT, one atmosphere pressure, no convectional mixing. Distance (Z) is in centimeters, time (t) in seconds, diffusion constant is D. The equation is –

Z = the square root of (D x t)

D for O2 into CO2 is 0.16 cm squared/second

So, in the first second Z is 0.4 cm
First minute Z is 3.0 cm
First 5 minutes Z is 7.0 cm
First hour Z is 24 cm
Something is wrong here because gases diffuse far more quickly
than that. If you open a bottle of some smelly organic molecule
like benzene thiol it doesn't take minutes to travel to your nose,
and that's a much bigger and slower moving molecule than O2.
Anyway, these numbers would only apply with no flow of CO2,
just a static amount of CO2 in the keg.
Jim
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